In the prior art, there have been acoustic wave devices which utilize surface acoustic waves to transport liquid drops and other substances for transport. Acoustic wave devices which transport substances for transport comprise, for example as described in Patent Reference 1 below, a piezoelectric substrate which generates surface acoustic waves by means of the piezoelectric effect, on which is placed an excitation electrode to excite the surface acoustic waves. And, by applying high-frequency signals to this excitation electrode, surface acoustic waves are generated on the piezoelectric substrate, and a substance to be transported placed on the piezoelectric substrate is caused to be displaced. Surface acoustic waves (SAWs) are waves comprising longitudinal waves and transverse waves, and propagate on the surface of an elastic body. The piezoelectric effect is a phenomenon in which, when a force or an electric field is applied to quartz or another crystal, a voltage or strain occurs corresponding to the stress or to the electric field.    Patent Reference 1: Japanese Patent Application Laid-open No. 2006-248751
However, in an acoustic wave device which transports substances for transport in this way, in order to place a substance to be transported on a piezoelectric substrate and transport the substance, the transport path over which the substance to be transported is transported must be cleaned each time a substance to be transported is transported. In particular, when the substrate for transport is a liquid, a portion of the substance to be transported which has been transported on the transport path easily remains, and the task of cleaning is troublesome. Hence there has been the problem that the efficiency of the overall task of transporting a substance to be transported by means of an acoustic device is poor. Further, transport of a substance to be transported having properties which cause degradation of or damage to the piezoelectric substrate is difficult, and so there has been the problem that the range of selection of substances for transport is effectively limited.
Further, in an acoustic wave device of the prior art, it has not been possible to simultaneously transport two or more substances for transport existing physically separated along the direction of propagation of surface acoustic waves. This is attributed to attenuation of surface acoustic waves due to substances for transport positioned on the upstream side of the propagation of surface acoustic waves. As a result, there has also been the problem that the range of application and fields of application of acoustic wave devices have been limited.
In order to mitigate the trouble involved in the task of cleaning the transport path, Patent Reference 2 below proposes a acoustic wave device in which a sensing region, which detects the physical quantity of the substance to be transported on the transport path of the substance to be transported is provided on the piezoelectric substrate, and moreover an excitation electrode is comprised to provide cleaning liquid to the transport path and the sensing region. However, merely causing cleaning liquid to pass through the transport path and sensing region does not result in an adequate cleaning effect, and moreover a task to remove the cleaning liquid remaining on the transport path and sensing region becomes necessary, so that this proposal is insufficient as means of resolution to mitigate the trouble of the cleaning task.    Patent Reference 2: Japanese Patent Application Laid-open No. 2006-226942